Variable speed for a mill/drill

[Gadabout]

Hi All, I have a rather oldish asian mill drill head and column grafted onto a Centec 2A automill setup up with 4 axis cnc. I find climbing a step ladder or using a stool to get up and change the belts for a speed change rather tedious and as I get older more painful, so I considered changing the belt setup to variable sheaves etc but now not sure if going to a vfd and a  new three phase motor might be the best option? I would like Mach 3 to be able to start and stop the motor and to control the speed, is this possible. I would like to keep the vfd/ motor conversion to about $500 and as I am in OZ can someone suggest what parts would be best to buy?
thanks

Mark

[tumutbound]

VFD and a 3 phase motor sounds like the easiest way to go. Mach 3 can control the motor start/stop and speed.
What power is the current motor?

[Gadabout]

Hi, Its 750 watt single phase 240 volts, only have single phase here at home, did find in my storage area a 3/4 horsepower three phase ( sorry to mix watts and horsepowers but wanted to read direct from the labels), would this be powerful enough( I think not in my mind) to use?

cheers
Mark

[John Rudd]

Mark,
The general consensus is that a three ph motor is slightly more efficient than a single for the same hp...
That said, 3/4hp is 746*3/4 watts......
There is something else to consider....Is your motor a dual voltage motor?  I.e can it be configured for
Star and Delta?

[Gadabout]

John,
 All the motor has are three connections marked "A", "B", "C". The plate says 400/440 volts.
 I diddly squat about three phase motors

cheers
Mark

[BillTodd]

John,
 All the motor has are three connections marked "A", "B", "C". The plate says 400/440 volts.
 I diddly squat about three phase motors

cheers
Mark

You'll have to find the motor's star-point to convert that motor.

http://madmodder.net/index.php/topic,7773.msg83488.html#msg83488


One alternative is to convert a 400/500v VFD to work on 240v (not recommend ed unless you know what you are doing)

www.homeworkshop.org.uk/index.php?option=com_agora&task=topic&id=928&Itemid=47


I added a variable speed belt drive to my drill/mill using a scooter variator. It gives a 4:1 range and has the advantage of increasing torque at low speeds (a VFD will be at best constant torque and will probably be reduced at low speed)

My mod is completely manual so would need to be motorised for mach3 use.

http://wktodd.webspace.virginmedia.com/drillmill/


Bill

[Gadabout]

Bill, That all looks very impressive!
I think with my electrical skils I will be best looking for a new motor than trying to convert the one I have from star to delta considering that it is not really enough horsepower anyway. Just need to figure out what I need there are so many on Ebay .com.au that I don't know what will do the job for my needs

regards
Mark

[russ57]

It could be easier than that.  My vfd 'powtran' brand will  run a 440v motor
off 240v just by configuration.  I purchased it from eBay Australia,  18 months ago.
And I guess the power issue depends on what you intend cutting.

-Russell